Why am I suddenly receiving spam calendar invitations/appointments in Outlook (Microsoft 365 Family).

Microsoft is aware and didn’t even trying. I ported most of my main correspondence to Gmail, since their rules is more robust and catch those domains and keywords by totally deleting them.

I’m not going to renew Microsoft 365 end of this year. It is a shame. If its not for my xbox, I will totally delete my outlook.com account!

So basically, Microsoft's solution is not to improve their spam filter, but to make it's users create "rules" to filter out the spam that MS fails to stop? How many people, realistically, could follow these instructions and create rules? I've tried this "solution" by the way. These spammers have so many fake email addresses tied to one "spam" that the only way to create a rule that works is to use some of the words in the title. Even that fails most of the time. I finally gave up on rules. All the the steps mentioned to change calendar events settings failed. So far, reporting and choosing phishing is the only option that seems to be remotely working. Perhaps improve your spam filters instead of putting both the problem and the solution on your customers?

Here's the problem - I do not have these spam invitations in my Outlook Inbox on my PC, they are only appearing in the calendar on my phone. Is there a way to remove them from my phone?

Exactly. I've been told to delete/block the emails with these meeting invitations attached but there are no associated emails when I check, so there's nothing to block. The invites just appear in my calendar (both in outlook and in my phone's calendar)

Can't you use the approach I used on my PC? Uninstall the Microsoft Calendar from your phone and use GMail's calendar instead.

There's NO justification for Microsoft allowing push events being placed on our calendars without intentionally subscribing to an external source.